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The control of Rhodopsin expression patterns in
. (
A
) Transcriptional repressors restrict Rhodopsins to specific photoreceptor (PR) types. Defective proventriculus (Dve), which is expressed in outer PRs (R1-R6), represses and to allow exclusive expression of in outer PRs. Spalt (Sal) is expressed in the inner PRs (R7 and R8), where it represses . Finally, Prospero (Pros) prevents expression of R8 opsins ( and ) in R7s, whereas Senseless (Sens) prevents expression of in R8. These mechanisms thereby restrict Rh3 expression to R7, whereas R8 can only express Rh5 and Rh6. (
B
) The two main PR subtypes (p and y) are specified by a stochastic decision made independently in each R7. Stochastic Spineless (Ss) expression in ~70% of R7s (left) induces Rh4 and Dve expression and determines yR7 fate. Dve, in turn, represses , allowing exclusive expression in yR7. The other 30% of R7s (right) lack Ss and therefore acquire p identity and exclusively express . The coordination of p and y identities in R7 and R8 in each ommatidium is achieved by an unknown signal (blue arrow, right) sent by pR7. Ss represses this signal in yR7 (left), and in the underlying R8 the constitutively active Hippo (Hpo) tumor suppressor pathway specifies y identity by default. Warts (Wts), the nexus of the Hpo pathway, represses () and , and promotes expression. The pR7 signal instructs the underlying R8 to become pR8 (right), by inducing expression. Melted represses Warts expression, thereby disrupting Hpo pathway activity and allowing exclusive expression of Rh5. (
C
) The exclusion of Rh5 in yR8s requires two mechanisms: continued Hpo pathway activity (as shown in B) and negative feedback from Rh6 itself. This feedback also involves Gα, but not the other components of the canonical phototransduction pathway.

The TF network described above provides the context within which the p and y subtypes are established through a binary stochastic decision made independently by each R7 (
Fig. 3B
). Stochastic expression of the PAS domain-containing basic helix-loop-helix (bHLH) TF Spineless (Ss) in ~70% of R7s induces yR7 fate and expression of
Rh4
(
Wernet et al., 2006
). Ss also induces
dve
in yR7s to repress expression of
Rh3
, thus yielding exclusive expression of
Rh4
in yR7s. The remaining 30% of R7s, which lack Ss, acquire p identity and exclusively express
Rh3
. The resulting Rh3-Rh4 pattern in R7s is random (
Fig. 2B
) and differs from individual to individual and between the two retinas in the same animal (
Bell et al., 2007
), resembling the pattern of human long and medium-wavelength sensitive cone PRs (
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).

Hacienda Temozon
Driving through the small pueblo of Temozon Sur doesn't prepare you for the grandeur of the namesake estate, formerly a massive cattle ranch and, more recently, a major henequen manufacturer. The main house, a 16th-century, oxblood-coloured building, rises above manicured lawns and an unusually long swimming pool. As well as the reception and restaurant - which occupies an airy, brightly lit terrace with views over the pool - it contains the library, and a series of small common rooms, used for afternoon tea and evening cocktails. Photographs show images of former Mexican presidents strolling along Temozon's shady arcades with Bill Clinton and George G Bush, who attended summits at the hacienda; Colombian singer Shakira was also a recent guest. The 28 rooms range from small, rustic, cabaña-style villas to cool, high-ceilinged rooms with their own hammocks, and a presidential suite - once the home of the hacienda's owners - that has a beautiful stone bathtub, terrace and private garden. Quirkier aspects of Temozon include a spa that provides massage and other treatments in underground caves and, a 45-minute walk from the estate, a cenote or sink hole where guests can bathe in total seclusion.
IN THE AREA
A short drive north along the main Uxmal-Mérida highway takes you to the Hacienda Yaxcopoil (www.yaxcopoil.com): with only one bedroom and no restaurant it's not a recommended property for overnight stays, but the extensive hacienda buildings are very atmospheric. The archaeological site of Uxmal, one of the most important in Yucatán, is also within driving distance.
PRICE
Doubles from US$285
CONTACT
Temozon Sur, Km 182 Carretera Mérida-Uzmal, Yucatán (00 52 999 923 80 89;
www.thehaciendas.com
) Pictured: Temozon's long swimming pool.

Hacienda Temozon

Hacienda Teya

Hacienda Teya
Founded in 1683 by the magnificently named Doña Ildefonsa Antonia Marcos Bermejo Calderón y de la Helguera, the wife of the Count of Miraflores, Teya was a cattle ranch and farm until the henequen boom of the 19th century. The main house, with its colonial baroque entrance and belfry, resembles the façades of the churches you see around the peninsula, while the machine house is now a spacious salon with an indoor pool. With just six suites, Teya has a more intimate feel than some of the more imposing estates, and the orchards and botanical gardens are lovely for a pre-dinner stroll. The restaurant, serving Yucatecan cuisine, is justifiably famous, and diners have included Hillary Clinton and Spain's Queen Sophia.
IN THE AREA
The city of Mérida is minutes away by car and, while shabby around the edges, it is well worth exploring for its handsome plazas and busy shopping area. Tixcokob, a small town just north of Teya, has a pretty convent and is on the so-called 'cenote belt', along which are several sinkholes open to the public.
PRICE
Doubles from 1,044 pesos (about £50)
CONTACT
Km 12.5 Carretera, Mérida-Cancún (00 52 999 988 0800;
www.haciendateya.com
) Pictured: Saturday night dancing in Mérida.